Perception

Object recognition becomes difficult when the main axis of the object is foreshortened. It has previously been reported that this so-called foreshortened disadvantage is larger when the silhouette of the object is presented than when the line drawing of the object is presented. The pronounced foreshortened disadvantage in silhouette recognition indicates that the internal details of the object, which are absent in the silhouette, provide useful information, particularly when the main axis is foreshortened. But the role of these internal details remains controversial. One account for the pronounced disadvantage is that the internal details contribute to the derivation of the main axis. The other account is that internal details provide the distinctive features that are directly matched to the object represented in memory. The aim in the present study was to determine which of these two explanations best accounts for the differential foreshortened disadvantage between line drawings and silhouettes. To reduce the uncertainty regarding the axis orientation, a 3-D arrow indicating the orientation of the main axis was presented as a cue before the object itself was presented. As a result, the difference in the foreshortened disadvantage between silhouettes and line drawings disappeared. This indicated that the pronounced foreshortened disadvantage for silhouettes was caused by a lack of axis information. In other words, the internal details provided the information necessary for axis derivation when the axis was foreshortened.

Casual observation suggests that pigeons and other animals can recognize occluded objects; yet laboratory research has thus far failed to show that pigeons can do so. In a series of experiments, we investigated pigeons' ability to ‘name’ shaded, textured stimuli by associating each with a different response. After first learning to recognize four unoccluded objects, pigeons had to recognize the objects when they were partially occluded by another surface or when they were placed on top of another surface; in each case, recognition was weak. Following training with the unoccluded stimuli and with the stimuli placed on top of the occluder, pigeons' recognition of occluded objects dramatically improved. Pigeons' improved recognition of occluded objects was not limited to the trained objects but transferred to novel objects as well. Evidently, the recognition of occluded objects requires pigeons to learn to discriminate the object from the occluder; once this discrimination is mastered, occluded objects can be better recognized.

Previous work with non-human species has shown that eyespots function as sign stimuli for defensive behaviour. But it is unknown to what extent eyespots are a dominant feature of objects for human perceptual responses. We examined whether young children perceive eyespots as a dominant object feature. One hundred and nineteen children from the first, second, and third grades were presented with small manikins, called “Joopes” that varied in the number, type, and arrangement of facial features. Four kinds of Joope heads were used: single element (eyes, mouth, or beak only), monovalent (spatially concordant eyes and mouth, or eyes and beak), ambivalent (asymmetrical eyes and beak, or eyes and mouth), and cyclopean (single eye with orthogonal beak). Two task groups (Peepers and Gobs) ‘helped’ the Joopes to either ‘see’ their food or ‘eat’ it, by placing food in one of 24 feeding dishes. Results indicated that responses made to the ambivalent Joopes differed, with greater ‘drift’ shown by the ‘eating’ group towards the ‘seeing’ responses than by the ‘seeing’ group towards the ‘eating’ responses. The dominant role of eyespots was thus confirmed for children in the second and third grades, but response inconsistencies in the youngest group suggested difficulties in handling incongruent stimuli. The implications of these results for understanding basic perceptual processes are discussed.

It has been well established that vertical disparity is involved in perception of the three-dimensional layout of a visual scene. The goal of this paper was to examine whether vertical disparities can alter perceived direction. We dissociated the common relationship between vertical disparity and the stimulus direction by applying a vertical magnification to the image presented to one eye. We used a staircase paradigm to measure whether perceived straight-ahead depended on the amount of vertical magnification in the stimulus. Subjects judged whether a test dot was flashed to either the left or the right side of straight-ahead. We found that perceived straight-ahead did indeed depend on the amount of vertical magnification but only after subjects adapted (for 5 min) to vertical scale (and only in five out of nine subjects). We argue that vertical disparity is a factor in the calibration of the relationship between eye-position signals and perceived direction.

In the present study, participants searched for a conjunction of color and orientation either from the same part of an object (same-part display), or from different parts of an object (different-part display). While no difference was found between the two display conditions in single feature searches, conjunction search in the same-part display was significantly faster than that in the different-part display. This same-part advantage applies to both the inner part as well as the outer part of an object. These results suggest that features are more readily integrated if they are from the same part of an object than if they are from different parts of an object. The formation of object part representations thus influences how features are integrated and encoded during visual information processing.

We investigated whether the learning of colour terms in childhood is constrained by a developmental order of acquisition as predicted by Berlin and Kay [1969 Basic Color Terms (Berkeley, CA: University of California Press)]. Forty-three children, aged between 2 and 5 years and grouped according to language ability, were given two tasks testing colour conceptualisation. Colour comprehension was assessed in a spoken-word-to-colour-matching task in which a target colour was presented in conjunction with two distractor colours. Colour naming was measured in an explicit naming task in which colours were presented individually for oral naming. Results showed that children's knowledge of basic-colour terms varied across tasks and language age, providing little support for a systematic developmental order. In addition, we found only limited support for an advantage for the conceptualisation of primary (red, green, blue, yellow, black, white) compared to non-primary colour terms across tasks and language age. Instead, our data suggest that children acquire reliable knowledge of nine basic colours within a 3-month period (35.6 to 39.5 months) after which there is a considerable lag of up to 9 months before accurate knowledge of the final two colours (brown and grey) is acquired. We propose that children acquire colour term knowledge in two distinct time frames that reflect the establishment of, first, the exterior (yellow, blue, black, green, white, pink, orange, red, and purple) and, second, the interior structure (brown and grey) of conceptual colour space. These results fail to provide significant support for the order predicted by Berlin and Kay, and suggest, instead, that the development of colour term knowledge is largely unconstrained.

Interviews with a multilingual synesthete (MLS), who experiences colored letters for Roman and Cyrillic alphabets and for digits, revealed stable synesthetic experiences over 2½ – 5 years. Colors of Cyrillic letters were based on Roman letters. Four Stroop tests involving both types of letters showed that MLS was able to name print color faster if the colors matched her synesthetic colors, showing that synesthesia is automatic. Letter-naming times for blocks of color were slower than those of actual letters, supporting unidirectionality of synesthesia. Stroop tests with Roman, but not Cyrillic, letters showed MLS acquired new temporary letter–color pairings and her color-naming times for these were not different from those for her original synesthetic colors.

The aim of the study was to examine the effects of differences in temporal gating and ear of presentation (both separately and in combination) on listeners' ability to detect an increment in the level of a 1 kHz component (the target) relative to that of four spectrally flanking components. The flanking components were always presented to the listeners' right ear, while the target component was either presented to the same ear (monaural presentation) or to the left ear (dichotic presentation). Similarly, the target and flanking components were either gated on and off at the same time (synchronous presentation), or else the target component began 100 ms before and terminated 100 ms after the four flanking components (asynchronous presentation). On average, thresholds were lowest in the synchronous, monaural condition, and highest in the two asynchronous conditions. Ear differences alone did result in elevated thresholds for most listeners. However, combining differences in gating and ear of presentation produced thresholds that were indistinguishable from those obtained when gating differences alone were employed. These results are consistent with the suggestion that differences in temporal gating lead to more complete segregation of concurrent frequency components than differences in spatial location.